Weight, Body fat and BMI.


Weight

First of all let me begin with the plain and simple weight, a common number that everyone at some point in their lives has probably checked. Its simple, you check your weight you get a figure and if you want to lose weight you try and get that figure lower through exercise and diet.

BMI

BMI or (body mass index) is a way of measuring what body type category you are. The basic categories are underweight, average, overweight and obese. By using your weight and your height you can use a simple equation to give you a BMI number. There is a big problem with this method in that it does not take into account what your body weight is composed of.

For example:

Weight divided by height = X

X divided by height again = BMI

115.1kg/1.78m = 64.7

64.7/1.78 = 36.3 

BMI is 36.3 


As can be seen from the table this BMI is in the obese catagory but for someone who is exactly the same height and weight but very muscular and a low body fat percentage would still come up as obese which doesnt make sense, how can you be obese with no fat? For the majority of people though the BMI calculation would be sufficient.
Body fat percetage

This leads me onto a more accurate way to really tell if you’re loosing weight or not, Body fat percentage. This is a measurement of the amount of fat that any person has on their body. There are a few different ways that this can be done but im going to focus on the 3 main ways.
1. Skin calipers
2. Bioelectrical impedance

3. Hydrostatic weighing

Skin calipers


Skin calipers are definately the cheapest way to measure your body fat %. They can be purchased for under £5. It will come with instructions but basically you pinch the skin an inch above your hip squeeze the calipers and an arrow will point to a number. (See video at bottom) This number can then be used along with your age to look at a chart which will tell you appoximately your body fat %. 

For example:

Skin fold measurement of 26mm for a 31-35yr old male would be about 25.5%. From looking at the chart you can see that 25.5% of that persons weight is fat and they are overweight.

Bioelectrical impedance

Bioelectrical impedance isnt as bad as it sounds. They are either handheld or available on a set of scales and it works by sending a weak electrical signal through your body and the computer calculates you body fat. You cant feel it and its painless. By far the easiest of the three to do but is also the most inaccurate. These are also quite cheap and affordable to purchase from £5-£30.
Hydrostatic weighing

The last of the three is the most accurate but also the most expensive costing from £100, Hydrostatic weighing. Firstly ill start of by saying that only specialist places wil be able to do this. You will be weighed normally then you will be weighed completely submerged in a water tank. These two figures are then used to create a very accurate reading of the body fat %.

Summary

Overall id say that a skin caliper is the best option to go with, its cheap and easy to do by yourself and it also gives you that little bit more information about if you are actually loosing weight (as in fat) as weight can change due to other factors like building muscle. 

There is a simple equation that can be used to find out exactly how much body fat you have in weight compared to non-fat body weight. 

Eg. Male weighs 100kg and has fat % of 15%
BW=body weight, BF%=body fat %, BFW=body fat weight

BW/100xBF%=BFW
BW-BFW=NON-BFW

100/100×15=15kg body fat weight
100-15=85kg non body fat weight

Repeat this equation everytime you measure/weigh yourself and you can see if the actual fat weight is getting smaller.

A quick video i found on youtube on how to use a skin caliper.

https://youtu.be/e8x1rj3p-sI

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